The present invention generally relates to a crankcase ventilating system and more particularly, to an improved breather arrangement for relieving or stabilizing pressure variation within a crankcase of a V-type internal combustion engine of an OHC (Overhead cam shaft) system.
Commonly, in a reciprocating type internal combustion engine, there is a tendency that the pressure within a crankcase varies according to revolutions of the engine due to an increase in a leakage amount of the so-called blow-by gas which leaks out from combustion chambers into the crankcase through clearances between piston rings and cylinder walls in the explosion and expansion strokes, and also, due to a pumping action of pistons, etc. Accordingly, in the case where the interior of the crankcase is directly communicated with an intake passage so as to subject the blow-by gas within the crankcase to combustion in the combustion chambers simultaneously with a combustible charge, oil contained in the blow-by gas is brought into the intake passage by a large amount, following the pressure variation within the crankcase, thus resulting in such a problem that the oil consumption is undesirably increased. Therefore, there has been employed a breather arrangement which is adapted to alleviate the pressure variation within the crankcase by providing a breather chamber (i.e. a pressure buffer chamber) communicated with the interior of the crankcase.
Incidentally, as a breather arrangement of the above described kind for a V-type engine, there has conventionally been proposed, for example, in Japanese Patent Publication Tokkosho No. 52-39983, an arrangement in which cavities as breather chambers are formed by casting at outer sides of both inclined banks for the engine crankcase.
In the known arrangement as described above, however, since the breather chambers are formed at the respective outer sides of the inclined banks, if the volume of each of the breather chambers is increased in order to improve an oil separating function thereof with respect to the blow-by gas, the portions for the breather chambers are expanded outwardly to increase the engine dimensions and consequently, installation of various auxiliary appliances at the side portions of the engine is undesirably limited. The disadvantage as described above is particularly conspicuous in the V-type engine of the OHC system in which the amount of leakage of the blow-by gas tends to be large owing to high speed revolutions.